Biostratigraphy And Paleoenvironment Of Deposition Of Bima And Gongila Formations In M-1 Well Bornu Basin Northeastern Nigeria.

ABSTRACT Two lithofacies units were delineated in the studied well section. The lower part shows intercalation of shaly gypsum and shale with preponderance of shaly gypsum which has never been attributed to Bima Formation the thick shale sequence at the upper part represents the Gongila Formation characterized by thin intercalated shaly gypsum lying unconformably on Bima Formation. The Bima lithofacies might have been formed as a result of various factors such as basinal structure salinity ecology tropical climate and various processes of transportation and sedimentation. Two palynozones of Afropollis jardinus assemblage zone 1 characterized by co-occurrence of Forma PO 304 Lawal Afropollis jardinus Steevesipollenites binodosus and Hexaporotricolpites emelianovi dated Albian to Late Cenomanian belong to Bima Formation and Cretacaeiporites spp assemblage zone ll characterized by maximum development of Cretacaeiporate pollen - Cretacaeiporites scrabratus C. mulleri and C. polygonalis are established. Other forms diagnostically present are Triorites africaensis Elaterosporites klaszi Galeacornea causea and Gnetaceaepollenites clathratus. The zone is dated Late Cenomanian to Turonian age belonging to Gongila Formation. The paleoenvironment of deposition varies from marginal marine environment trough typical marine to marginal marine setting characterized by peridinacean forms at the base trough presence of microforam lining to long processes organic wall organism in the upper part of the section.